Electrical line testers are generally known to include the type having a light indicator which is lit when an electrified line is contacted, and another type having a voltage sensing circuit and readout dial indicating the voltage level of the electrified line. The light indicator type is intended to be of low cost and simple construction for use in confirming whether or not a line is electrified with a standard line voltage, e.g., 110 volts AC. However, it has the disadvantage that the light indicator is often difficult to see in bright daylight conditions. Also, the light becomes lit for any voltage over the threshold level, and therefore does not distinguish higher line voltages, such as 220 volts AC. On the other hand, voltage readout testers are quite expensive and bulky, and are not convenient to use and read, particularly in dark, cramped spaces.
Determination of voltage through a line for such devices as high-voltage railroad "third rail" warning detectors are expensive and have complicated electrical schemes. They are intended to be permanently installed. Other detection devices are expensive in that they employ two or more different threshold detecting devices to ascertain different voltages. In addition, the method of warning, once voltage is detected, is complicated. Multiple tone generator circuits which include a pulse train source and digital gates are required to generate different tones.
In general, complicated wiring diagrams characterize the existing voltage detection and multiple tone generating devices. They all require some combination of diodes, rectifiers, amplifiers, display units, annunciators, strobe lights, oscillators, transistors, capacitors, resistors, transducers, pulsators, transient protectors, ground isolations, multiple gates, integrated circuits, anodes, cathodes, electrodes, and emitters or they require the user to manipulate switches to properly operate the device.
Accordingly, it is a principal object of the invention to provide an electrical line tester that can be easily used by one person that is of low cost, of simple construction, small and light enough to be conveniently held in the hand or worn on the belt and carried into small, cramped, dark places, and which provides an unmistakable signal to the user of the voltage level of an electrified line in both bright daylight conditions and dark, cramped conditions. It is a further object that the line tester of the invention distinguishes between different line voltages without the user having to read a dial.